Just a tid-bit from "Dear Timothy - Letters on Pastoral Ministry".
"The key that unlocks the biblical outlook is the perception that the real subject of the Holy Scripture is not man and his religion, but God and his glory; from which it follows that God is the real subject of every text, and must therefore be the real subject of every expository sermon." - JI Packer1
1. JI Packer, Shorter Writing, 3:274-5, taken from Roger Ellsworth, Preach the Word, Dear Timothy - Letters on Pastoral Ministry, Founders Press, 2004, 275-6